In electronic devices such as cellular phones, telephones, PDAs and digital cameras, a variety of functions are added by inserting an IC card with a built-in memory or control IC, such as a SIM (subscriber identity module) card, an MMC (multimedia card), a Smart Media (trademark), an SD (super density or secure digital) card and a Memory Stick (trademark).
As the number of kinds of IC cards has increased in recent years, a variety of standards as to the card thickness have come into use.
Of these IC cards, the MMC card for example has an external view as shown in FIG. 16 and FIGS. 17A, 17B.
As shown in FIG. 16 and FIGS. 17A, 17B, the MMC card 10 has a card body 11 with a predetermined thickness a, which has a virtually triangular cut-off corner portion 12 at its front right corner to prevent its erroneous insertion. On the front side of the bottom surface of the card body 11 there are a plurality of contact pads 13 connected to an IC circuit inside the card.
The SD card 20 with a larger thickness b than the MMC card 10 has a construction as shown in FIG. 18 and FIGS. 19A, 19B and 19C.
As shown in FIG. 18 and FIGS. 19A, 19B, 19C, the SD card 20 has an upper body portion 21 with virtually the same thickness a as the card body 11 of the MMC card 10. On the back surface of the upper body portion 21 is formed a lower body portion 23 with a predetermined thickness which has a slightly narrower width than the upper body portion 21. That is, the SD card 20 has formed along both card side edges step portions 27 that are defined by the bottom surfaces of the upper body portion 21 and the lower body portion 23. The thickness b of SD card 20 is thicker than the thickness a of the MMC card 10. The upper body portion 21 and the lower body portion 23 have a cut-off corner portion 22 at their front right corner to prevent erroneous insertion.
On the front side of the lower body portion 23 a plurality of recessed portions 24 are formed, separated from each other by a plurality of partition walls 29. In these recessed portions 24 are arranged contact pads 25 connected to an IC circuit inside the card. The depth of each recessed portion 24 is almost equal to the height of the lower body portion 23 and therefore the surface of each contact pad 25 is spaced from the front surface of the upper body portion 21 by a distance equal to the thickness a of the upper body portion 21.
The connector for removably receiving such an IC card has a plurality of contact terminals made from metal leaf springs in a connector housing. The inserted IC card is electrically connected to the electronic device, on which the connector is mounted, by these contact terminals coming into contact with the contact pads formed on the front or back surface of the inserted IC card. The contact pads of the IC card include a plurality of power supply terminals connected to power supply lines and a plurality of signal terminals for transmitting/receiving of various signals. They are connected through the contact terminals of the card connector to power supply circuits and various signal processing circuits on the electronic device.
When considering a connector shared for receiving two kinds of IC cards with different thicknesses measured from the card surface to the card bottom surface, in this connector structure, each of these different cards is generally supported at its bottom surface by the connector housing.
In the connector housing structure that supports the bottom surface of each of these cards, however, because the cards have different thicknesses, when these cards are inserted, the distances from the contact pads of each card to the contact terminals of the connector differ.
Hence, if the elastic force (contact pressure) of the contact terminals is set to conform to a thicker card, a required contact pressure cannot be given to the contact terminals when a thinner card is inserted.
Conversely, if the contact pressure of the contact terminals is set to conform to a thinner card, when a thick card is inserted, the contact terminals deflect excessively beyond the stress limit, resulting in plastic deformations of the contact pieces.
The card connectors of this type are often equipped with an eject mechanism for extracting the card from the connector.
In this eject mechanism, an elastically displaceable braking piece is pressed against the card to produce a friction force acting in a direction opposite that in which the card is ejected, in order to prevent the card from being pushed out rapidly and falling from the connector.
When considering providing a card rapid ejection prevention braking piece in a common connector that can receive two kinds of IC cards with different thicknesses, it is common practice to arrange the braking piece in said common connector so that it engages the bottom surface of each card.
However, with the braking piece arranged to engage the bottom surface of each card, when a card with a different thickness is inserted as described above, the distance from the card bottom surface to the support surface that rigidly supports the braking piece changes.
Hence, if the elastic displacement (contact pressure) of the braking piece is set to produce an appropriate friction force for the thick card, the contact pressure and the resulting frictional force are too small for the thin card, making it impossible to provide the card with an appropriate friction force.
Conversely, if the elastic displacement (contact pressure) of the braking piece is set to produce an appropriate friction force for the thin card, the insertion of a thick card causes the braking piece to deflect excessively beyond the stress limit, resulting in the braking piece being plastically deformed.
The present invention has been accomplished under these circumstances and it is an object of the present invention to solve the above-described problems by providing a card connector which can receive two kinds of cards with different thicknesses with the same contact pressures while securing a sufficient reliability of contact between the contact pads and the contact terminals.
Further, it is another object of the present invention to solve the above-described problems by providing a card connector which can apply appropriate braking forces to two kinds of cards with different thicknesses and thereby reliably prevent an uncontrolled rapid card ejection.